Regeneration and promotion of catalytic activity of zeolites for DME conversion to olefin

Regeneration of H-ZSM-5 catalyst was tested on dimethyl ether (DME) conversion to olefin. The catalyst life was stabilized by the regeneration for a number of reactions. Since the decreases in both acid amount and surface area were observed, the regeneration must cause the change of structure, that is, dealumination. To confirm this assumption, dealuminated H-ZSM-5 was synthesized by steaming treatment so that the catalyst life was prolonged. The dealumination from zeolite framework proceeded via the formation of "unstable Al species" and their transformation to extra-framework. The change in HCl/Si molar ratio and preheating treatment influenced the particle size of MFI-type ferrisilicates (FeMFI), whose catalyst lifetime increased due to a decrease in size or an increase in acid site density. The introduction of Fe³⁺ in substitution for Al3⁺ enhanced light olefin selectivity. This is an abstract of a paper presented at the 23rd Annual Saudi-Japan Symposium on Catalysts in Petroleum Refining and Petrochemicals 2013 (Dhahran, Saudi Arabia 12/2-3/2013).